Burner safety control device



Sept. 12, 1950 J. 1.. HARRIS 2,521,717

BURNER SAFETY CONTROL DEVICE Filed Dec. 28, 1946 5 Sheets-Sheet 1 INVENTOR. John L. Hark/s Sept. 12, 1950 I J. HARRIS I 2,521,717

I BURNER SAFETY CONTROL DEVICE Flled Dec. 28, 1946 5 Sheets-Sheet 2 IN V EN TOR.

John L. Harris BY Sept. 12, 1950 J. 1;. HARRIS 2,521,717

BURNER SAFETY CONTROL DEVICE Filed Dec. 28, 1946 5 Sheets-Sheet 3 IN V EN TOR.

@ John L. Harr/ls Sept. 12, 1950 J. L. HARRIS 2,521,717

BURNER SAFETY CONTROL DEVICE Filed Dec. 28, 1946 5 Sheets-Sheet 4 INVENTOR. John 1. Harp/Ls WWW P 1950 J. L. HARRHS 2,521,717

BURNER SAFETY CONTROL DEVICE Filed Dec. 28, 1946 5 Sheets-Sheet 5 13 1.? \\Z\ I! F1 3. 9. K70

M H {24 4 93 I 107 123 92 I 58 120 9/ l 62 J 125 I? Fi g. 10. 122 (/0 INVENTOR. John L. Harv/ls Patented Sept. 12, 1950 2,521,117 BURNER SAFETY CONTROL DEVICE John L. Harris, Whitefish Bay, Wis., assignor to Perfex Corporation, Milwaukee, Wis., a corporation of Wisconsin Application December 28, 1946, Serial No. 719,100

22 Claims.

This invention relates generally to temperature control systems and apparatus, and more particularly to a system and apparatus for controlling the various operating cycles of a space heat ing furnace using oil or other fluid as a fuel.

In general, a combustible mixture of oil or other suitable fluid fuel and air (hereinafter referred to as fuel) is introduced into the combustion chamber of a furnace through a suitable appa-- ratus which usually includes, in the case of oil, a motor-driven pump and blower, hereinafter referred to as a burner or fuel supplying means. The burner delivers the oil into the furnace in finely divided particles forming a readily ignitible mixture. Placed near the burner is some means for igniting the combustible mixture discharged therefrom, hereinafter referred to as an igniter. The igniter may consist of a Wire which upon passage of electric current therethrough is heated to the ignition temperature of the fuel. It will be readily understood that ignition must take place simultaneously with, or at least very shortly after, the introduction of the fuel into the combustion chamber of the furnace. To delay ignition would allow too great a concentration of fuel to build up in the combustion chamber, which, when ignition did finally occur, might explode, causing considerable damage. After initial ignition has taken place, the igniter has served its purpose and may thereupon be made inoperative. With the burner delivering fuel to the furnace and the fuel burning at the desired rate, if for some unforeseen reason, such as failure of air supply to the burner or momentary fuel stoppage, combustion should cease, hereinafter referred to as flame failure, further operation of the burner would cause thefurnace combustion chamber to be filled withunburned fuel in such a concentration as to present a highly dangerous explosion hazard. In order, therefore, for a space or room .tobe properly and safely heated by a fluid fuel burning furnace, a room thermostat, a thermostat responding to the temperature of combustion, the burner, and an igniter must be so interconnected as to cause the burner and igniter to operate in proper sequence and to shut down when explosion danger exists. Under some conditions it is desirable that the control device which so interconnects the above mentioned elements should shut off the burner upon ignition failure, should shut off the burner on flame failure, then automatically recycle, placing the furnace back in operation shortly thereafter,

and if upon recycling, proper combustion still does not occur, should move to a position preventing further recycling (this position is hereinafter referred toas safety shut down) It has proved advantageous to also provide a resetting mecha-, nism, manually actuated, for resetting the control device after a safety shut down, permitting the structed and combined in a novel manner affording a simplified, compact, and durable mechanism for safely and efiiciently operating a fuel burning heating apparatus.

Another object of this invention is to provide a control device with an improved manual reset mechanism for placing the furnace back in operation after safety shutdown, but effectively preventing the furnace from operating as long as the reset mechanism is in actuated or reset position.

' Another object of this invention is to provide a control device incorporating means for limiting the period during which the igniter is at or above the fuel combustion temperature.

, Another object of this invention is to provide a control system incorporating parts constructed and combined in a manner affording timed operation of an ignition means, recycling in the event of a power or flame failure, and safety shutdown through the medium of a single combus tion responsive element and of a single heater actuated warp element.

More particularly, the present invention contemplates and has as a further object the provision of a control mechanism incorporating a relay controlled switch positionable to initiate I combustion in response to a demand for heat and to terminate combustion when the demand for heatis satisfied, a single combustion responsive element, a single heater actuated warp element. and a manual reset member constructed and combined in a manner affording timed operresetting position, the relay is incapable of positioning the switch controlled thereby to initiate combustion. 'in addition, it is also contemplated that the parts he so constructed and combined that once the relay is positioned to initiate combustion, an actuation of the manual reset mechanism will not effect a termination of such operation.

The constructiom.application and operation of;

mechanism embodying the. present invention will become readily apparent as the disclosure progresses and particularly points out additional objects and features considered of sp ecial ilnpqljt ance. And accordingly this invention maybe considered as comprising a system. dZonrnechanism, combinations and sula cotn 1 corporating parts constructed and combmed as hereinafter more fully et forth inthe description and appended claims, reference being had to the accompanying drawing illustrating but oneaeni bodiment of the invention and in which:

g-., 1 .is .a perspective rear..view ;of ,a portion) of the. control device. embodying, .thainvention,

ations; 1-.

with; a portion. of the casing cut; away to. better.

Show the arrangement of. parts mountedtherein, the, parts being shown inthe. positions assumed I when .a demand for heat. satisfied Fig.2 is. a. .view similar to Fig. 1 showing the parts in the. .positionsassumed during normal. operation in response .to-. -a,,demand for.';heat;-.

Fig. .3 is. a .view similar .to..F.'i g.;1 showing the parts in the .positions assume d immediately-f0l-1..

lowing a name. failure but' .priprlto .deenergization of the rela and conseqi ent opening, of the...

r ay conta ts;

Fig.4 is a iew. slmilai to Fig. 1 showing the,

part in safety shut-down, position;

Fig-.5 isa perspectivefront view oithe, control device .with .the. front cover. removed Fig. 6 is a view similar to Fig. 5..with .the front. coverin place;

Fig. .7 a sectionalview. .talren generally. along line,VI IVII of FigLjfiwithallparts exceptthose relating to the combpstion responsiye, element re moved. and with a, rearwardly extending -tubular piece only. partially. .in section Fig. 8 is an enlarged detailed view of a slip.

friction .connection between a combustion, re, sponsive element. and .a notched-arm .whose relative ..position within thecontrol-device .is .best

shown in Figs. 1 to 4;

.9. is a sectio al .viewtaken generally along Iine IX -IXof Fig. 6 fwiththe basev plate and all parts, except those relating to the reset vm ech-. anism, removed;

FigLlO is a .viewsimilarl to Fig.9, butwith the resetmechanism in actuatedori reset position; s

Fig. 11 is a schematic wiring diagranr of a term perature control system utilizing the control. deviceshown in Figs. .1 to.4..

Referring. now to.. Fig. 1, in which is shown,

a casing, IS with twooutwardly extendingmounting lugs. H and... [2, the. inner. side of the front wall of easing. l0. ispartially. covered. by aplate !3 de tacha bly, fastened thereto, as. will be demanner. and, is. provided with, two inwardly extending, vertically. spaced. portions. I1 and-16;

Portion l,8.is provided withan. internally threaded hole theretl roughreceiving an adjustable stop v memberm. Portionl'l mountsaninwardly proj ecting extension 20 to which is attached, one end.

of a spring ill. The other end of the spring 2! is fastened to the adjacent end of a plate 23 having a pair of opposed parallel ears 24 (only one of which is shown) provided with aligned holes through which extends a rigid pin 25 having one endfiigedly supportedly mounted-on bracket base 15 inany suitable manner.. The holes in the cars 24 and pin 25 provide a pivot mounting for plate Z 5, which is biased in a counter-clockwise direction by the action of spring 2|. Two U-shaped temperature responsive members 26 and 21, having legs w ge-and- 66. .31 respectively, are secured to the-free'end'of the plate 23 in spaced generally-paral-lell relation with respect to each other ,byn eansof ricets 32 which pass through aligned openings in the lower end portions of legs 28, 3| andpla'tc and through spacers interposed between the legs and the plate. Leg 3| of temperature. responsive member 2?! rests against the justablefstop l9. Riveted-tothe temperaturere! sponsive member 26 ,isa U-shaped bracket 34 enclosing an electric heating element 35;. A strin-. 36 and a, resilient blade d'l, .carryingacontact 38,; are secured to Opposite sides of the freenendpor tion of leg 28 by'meansof rivets-and clamping;- bar .39.. Apin 4110f electrical insulating material has. an enlarged endv vportion thereof lpivotallw= mounted in any; suitable-manner .to the back sideof strip'36.

Secured by any suitablenmeansto the plate. i3 is a, rectangularly shaped bracket 4!- havingdn; warrlly. extending portions .42, 43, ,and 45. For; n, is ro id h.- an nte n r thread d e-m n n a r ed be 5 nst tute ing a stationary contact opposingv movable con tact 38.. Portion. 44 also mounts a permanent; magnet. 48 positioned-in opposed relation to the; enlarged free; end portion of strip 46 which funce tions asanarmature for magnet 48 A terminal 1 s,4&ext ns hr0 eh, a r n ul r o n n n thebase, of the bracket 4|;- and is electrically connected to the extending portion 46 by a CQIIQHQ-y tor 50.. Portion 42 has an internally threaded hole; ethr s zathr ad d c ntac cm mr ber..5l. A block .52 of electric; insulating material is secured in any suitable. -manner to extending; portion andmountaa plate 53 iii-spaced insulatedrelation with respect to portion. 46. A11 L-shapedv bracket 54 is iastened to the plate 53lbymeans] of screws 55. The upwardly extending portion of this bracket mounts erectengularly shaped. resilient hinge member 56 which extends upwardly therefrom. Secured to the upper or free end of hinge member 56, asby means of rivets and a clamping pad,-is an upwardly-extend-. ing bar.58 ,having-an opening therethroughloosely receiving pin 40. The free end of pin is pro-, vided with cap 5!} and a-spring;60-. surrounds an intermediate portion in opposed relation to ban. 58 and the enlarged endof; the pin so as toserve as a. lost motion connectionbetween the bar 56 and the temperatureresponsive member 26. Bar 58 is provided wi-th an internally threaded hole therethroughtnearthe free end thereof which mounts a threaded contact member 6|. A generally, rectangular: mounting plate 62 is, fixedly secured. in anysuitable manner to plate l3 and is provided.v with off-set portions 63,. 64, l and 65; oneof which, 63;, is electrically connected by con.-. ductor- 6'!; to a terminal; lug 66 projecting through an opening in the plate .62. Portion 64-hasaninternally threaded opening therethrough mounting a threaded contact member 69; A resilient blade 10 is secured to and forms an extension of; r.

ries an electrical contact 12 coactingly opposing member 6| on movable bar 58.

Referring now to Figs. 1 and 7, a U-shaped bracket is secured, as by screws I5, to the interior top wall of easing I8 with its legs I3 and I4 depended therefrom and provided with aligned holes rotatably supporting a hollow shaft I8. The end of shaft I8 extending through leg I3 is internally splined as indicated at I1 to receive the adjacent complementary splined end of the shaft I8 (shown in Fig. 7). Rigidly fastened to the rear portion of shaft I8 (as viewed in Figs. 1 to 4, 7 and 8) is a ratchet wheel I8, and loosely supported on the shaft I8 adjacent the ratchet wheel I9 is an arm 8I having three steps or notches, 82, 83, and 84 on the under or lower side thereof. Fastened to arm 8| in any suitable manner is a plate 85 having two resilient arms 81 and 88 extending therefrom, the free ends of which are adapted to frictionally engage the notched periphery of ratchet wheel I9 so that rotation of the'shaft 16 will effect an angular movement of the arm 8| as long as such movement is unimpeded. A limit pin 89 is rigidly fastened to and extends rearwardly from leg I3 into the path of resilient arm 88. After the ratchet wheel I9 and arm 8| have moved a short distance counter-clockwise (see Fig. 1) resilient arm 88 engages pin 88 and is lifted thereby out of frictional engagement with the ratchet wheel I9, thus stop-- ping the movement of the arm 8|, although shaft I6 and ratchet wheel I9 continue to turn. A clockwise rotation of the shaft I6 (see Fig. 3) cperates through the frictional engagement of the resilient arms 81 and 88 with the ratchet wheel 19 to move arm 8| in clockwise direction until it engages the end of bar 58. When in this position, resilient arms 8! and 88 will then. slip over the notched periphery of ratchet wheel I9, permitting shaft 16 to continue turning in clockwise direction.

Plate I3 has a portion cut away to expose a portion of the inner side of the front wall of casing I8 directly behind, to the left of, and beneath bracket leg I4. A conventional relay 8|, including an actuating coil enclosed in a casing 92, is secured to that inner side portion of the front wall of casing I8 which is exposed generally beneath bracket leg 14. Relay 9| also includes a movable armature 93 pivoted on resilient spring hinges 94 which are secured to casing 82 in any suitable manner and extend between similar outwardly bent cars 95 on armature 83 and a clamping piece 81, being secured therebetween by screws 88. An irregularly shaped block 99 of insulating material is provided with upturned edges and is secured to the armature 93 by means of screws I80. An L-shaped contact carrying arm I8| is mounted on the block 99 by means of screws I82 and carries at its free end two contacts I 83 and I84 adapted to bridge, when the relay coil is energized, threaded contact members 69 and BI, respectively, as shown in Fig. 2. Mounted on the armature 93 by screws or other means is a bracket I86 provided with an offset ear extending generally toward arm 8| and provided at its free end with an internally threaded hole therethrough mounting a screw I81. An upwardly bent member I88 is secured in any suitable manner to the underside of the arm 8| and extends in overlying relation with respect to the screw I81. Relay casing 92 is provided with an off-set arm portion I88 which is disposed in spaced generally parallel relation with respect to armature 83 and mounts a permanent magnet I I acting to move armature 93 toward same. A conventional transformer H2 is bolted or otherwise secured to that exposed inner wall surface portion of casing I8 just to the left of bracket leg 14 and has primary winding and secondary winding leads connected to elements within the easing as will be explained subsequently.

Referring now to Figs. 9 and 10, a bar II3 of electrical insulating material is secured to the bracket I88 by means of a resilient spring hinge IN, the spring hinge being secured to the bar I I3 and bracket I86 by any suitable means. The

free end of the bar II3 has fastened thereto an L shaped latch element H5 which is adapted to engage the free end of the bar 58 (see Fig. 9) under certain conditions. A push button or thrust pin II'I extends through a supporting collar H8, through a front cover H8, through a sleeve I22, through the front wall of the casing I8 but not through plate I3, and through aligned holes in an essentially U-shaped bracket IZI mounted by any suitable means to the exposed inner Wall surface of casing I8 generally below bracket leg I4 and above relay casing 82. A compression spring I28 surrounds thrust pin Ill and is disposed between a shoulder I25 thereon and the upper or inner leg of U-shaped bracket I2I. A slightly bowed resilient strip I23 is riveted at one of its ends to an extending portion I24 of the bracket I2I and has its free end abutting the bar II3. Spring I28 resists an inward movement of pin I I1 and it will be evident from the foregoing that when the pin H1 is disposed as shown in Fig. 10 the resilient strip I23 is forced against the bar I I3, causing the spring hinge II4 to flex and the latch I I5 to move out of engagement with the free end of the bar 58.

Referring now to Figs. 5 and '7, the casing I8 is mounted by means of lugs II and screws I26 on a base plate I2! which in turn is mounted on a plate I28 with spacers I38 interposed therebetween. manner to the rear face of the plate I28 and extends rearwardly therefrom in surrounding relation to the shaft I8. 'Rigidly attached to an extension of the tube ISI is one end of a helical element I32 responsive to changes in temperature of the furnace combustion chamber and adapted to be inserted therein when the control device is properly mounted adjacent the furnace combustion chamber. The other end of the helical element I32 is rigidly secured by any suitable means to the exposed end of shaft I8. It will be evident from the foregoing that a change in combustion chamber temperature will cause the helical.

element I32 to expand or contract, this expansion or contraction being transmitted to the shaft I8 and causing rotation thereof counter-clockwise upon expansion or heat increase, and clockwise upon. contraction or heat decrease, as viewed in Figs. 5 and 6.

The insulating plate I3 (see Fig. 5) is secured to the inner surface of the front wall of casing I8 by means of screws 584, the front wall of the casing having openings I35, I3!, and I31 out therein (of which openings I35 and I3! expose portions of plate I3) and having a. depressed portion I38 in which is disposed a relay mounting nut I38 and lock washer I48. The transformer II2 extends partially through the opening I38. The opening I 31 allows access to terminals I82 and I83 mounted on plate 53. The base plate I2! is provided with a forwardly extending portion I44 having openings I45 therein permitting A tube I3I is secured in any suitable I entry; of ereetricalnwiring to the-connectedtom-the terminals: "I42, 143,445., MT}, 14.8,andcl453 Referringvnowto ;-Fig.- 6,; the front; cover; I. I9

S1idSrDV9ltih8 casing. IDfiand the'forwardly-ex-. tending portion I44 of: the base plate I27 and has an -indented' portiongrihl within which suitablew identifying marking maybeinscribed. The thrustmay then flow through terminal I48, conductor 61, mounting plate 62, contacts BI and Inconductor 20I, the transformer primary winding 202 (Fig. 11.), conductor 203, the relay coil 204 (Fig.

11'), conductor 205, to terminal- Hi'i, and then.

back to the electrical current source. The secondary low voltage circuit maybe traced as follows: The transformer secondary winding 206 (Fig. 11), conductor 20?, terminal I42, an external connection is made from terminal I42 through a room thermostat 20,8 of conventional, type (Fig. 11) and back to terminal I43, from terminal I43, through conductor 200, heating element -35, and through conductor 2I0 back to. the transformer secondar winding 206 (Fig. 11)

Since terminal I48 is connected to the line source of electrical current, the burner motor circuit can be traced as follows: Terminal I48, conductor 51., relay contacts 63 and I03, relay contacts I04 and El, conductor 50, terminal I49 (Fig. 5), and from terminal I49 an external connection may be made to the burner motor 2I I- more fully explained.- Referring to Fig.1, the elements of the control device are shown in theposition assumed when the room thermostat. satisfied and both the burner and igniter areoff. When these conditions exist, (see also Fig.

11), the igniter contacts 38 and 46 and thesafety 1 switch contacts 3! and T2- are closed. However,.

relay coil 204 remains deenetrgized since the tran former IIZ isofthe-choke type, allowing current sufficient to energize the relay to pass through its primary winding. 202 only when its failure should occur, the combustionchamber.

temperature will begin to clecreaseandshaft 16 clockwise, which in turn has lifted arm SI out of engagement with the free end of bar 58'.

As the space adjacent the room thermostat:

cools to a temperature below a predetermined value, the room thermostat closes, completing the transformer secondary circuit through the heating element 35. With the transformer secondary circuit closed, relay 9| is energized, pivoting the armature 93 aboutits springa-hinges 94;, which.-

of bar 58.? The-heatingcapacity of element 35is so chosen that after a short time, for example.- 1 min.utes, the temperature responsive element- 2t -has expandedsufliciently to move contact '30" away" from contact 45, thereby breakingthei circuiteto the igniter 2I3. It may thus be'seem that. theigniterremains energized a period of time dependent onthe-heating capacity of heater.

35.: Magnet 48 causes'contacts 38 and 46- to'sep aratewith-a snap action in a conventional known" manner. Since-arm IJI is positioned so thatwits notch- 82 may-be engaged-by the free end of-bar 58,-the expansion of temperature responsive. element. 25 does not. move the bar 58 sufficiently to open safety switch contactsGI and 12'; such a-ctionr moves the-freeend of.-bar 58 into engagement-with notch :82 of arm GI, whereupon the continued movement of element 26 merely moves pin-:40 through the opening in bar 58=thereby compress ing spring-'69." Consequentlyrelay QI-remains; energized, thus holding its contacts I03 and IM; inbridging'engagement withcontacts 69 and 51:.

With relay contacts I03-, 69 and I04; 5 I'closed and:-

. igniter switch-contacts/sil and-t6 0pen,-the-.fur--- nace-is in normaloperation and the elementsofi' thecontrol device assume the positions shown'in Fig. '2.

After the room thermostat closes and the. relay. 9| isenergized, an electrical circuit: iscompleted to the burner and igniter. and combustion is not, initially estab1ished,-arm 8I- will remain-outzof engagement with the freeend- .of;:bar 58. After'the heating element 35 -has;

heated member =26 theignition contacts and.. 46 and safety switch. contacts 6 I and .12 will, be, opened with asnapaction. When contactsv 6| and-l2 are opened, relay BI is deenergized, stop-.- ping, the burner. The above mentioned. snap action and the resilient effect of the blade 10. causes the: free end of thebar. 58-to move to the.-

left (as viewed-in Fig. 1) beforemovement of.

relaylll. todeenergized position is completed;

consequently, latch II5 holds the free end of bar; 58 (seeFig. 11). and prevents cooling ofmember 26 fromagain closing contacts Hand 'IZand re cycling the controldevice. failure of. combustion-the controldevice will not. recycle; butwill assume safety shut down position.

If. during normal burner operation a flame-.-

willw bevrotated counter-clockwise, lifting arm, 0|

out.of engagement with the free end of bar..58.'v at the-notch 8,2. Assoonasthis occurs, spring 50,, which was placed. under considerable compression by the-heateractuated movement of member 2,6,T

willforce the free end of;bar 58 into engagement.- I

withnotched .portion83 of arm M, such further. movementof bar 58 being su-fiicientto opensafetyswitchcontacts GI-and 12- (see Fig. 3). safety switchjcontacts GI and I2 are'open, thetransformer primary circuit is broken and the,

relay file isdeenergized; thus breaking the burner.-

motor circuitythroughthe opening ofcontacts ;Ill3;.'

If the igniter f-ails Thus upon initial When I is, and I04, The deenergization of relay 9| also positions latch H5 in the path of the free end of bar 58, thus preventing any further movement of same toward notched portion 84 of arm 8|. In addition, heating element 35 is deenergized and begins to cool. In this connection it shouldibe noted that in Fig. 3 the elements of the control device are shown in the positions assumed just after the safety switch contacts GI and I2 have opened and relay contacts I03, 60 and I04, 5| are about to open.

As the heating element 35 cools, the temperature responsive member moves the igniter contact back into engagement with contact 46 and through pin moves safety switch contact 6| back into engagement with contact I2. Assuming that the room thermostat is still calling for heat and the transformer secondary circuit is therefore closed, relay ill will be immediately energized,

thus closing contacts Hill, 60 and I04, 5|, thereby closing the burner motor and igniter circuits. *If conditions causing the flame failure have been removed, the burner motor and igniter-will proceed through a normal heating cycle. and arm Bl will move into engagement with bar 58 as described previously with reference to Fig. 1. However, if combustion does not occur upon reclosing of the burner motor and igniter circuits, the furnace combustion chamber will continue to cool and arm BI will move to its extreme counterclockwise position (see Fig. 4). The burner motor and igniter will operate until heating element 35 causes temperature responsive element 26 to open igniter contacts 33 and 35, andsince arm "8| is in its extreme counter-clockwise position, as seen in Figure 4, the temperature responsive element 26 will move bar 5B into engagement with the arm 26 at notch 8d and will open the safety switch contacts El and i2. Opening contactsBi and "it breaks the transformer "primary circuit and deenergizes relay 9!. As the relay armature 93 moves to its deenergized positio it opens relay contacts E03, 69 and lu l, 5i, stopping the burner, and also moves the latch H5 into a retaining engagement with bar 53 thereby holding it in a position preventing reclosure of the Safety switch contacts GI and :2 as the heating element 35cools and igniter contacts 38 and 46 again close. With safety switch contacts iii and i2 and relay contacts its, $9 and I04, 5i all open, both theburner and igniter circuits are open, the elements of the control device assuming the positions shown in Fig. 4. The burner and igniter are now inoperative and the control device is in safety shut-down position.

To restart the burner and igniter the manual reset mechanism must be actuated. Referring now to Fig. 9, in which bar H3 and latch 5 are positioned as shown in Fig. 4, if thrust pin I I1 is manually depressed its inner end will engage the bowed resilient member I23, causing it to flex against the bar I I 3 pivoting the bar I I3 and latch i ll; out of engagement with contact carrying bar 58 (see Fig. 10). This allows the safety switch contacts SI and "I2 to close and the burner and igniterto tiereupon begin a normal cycle establishing combustion, as previously described with reference to Fig. 1. If the thrust pin I I1 were tied down in the actuated position by an inexperienced furnace attendant and relay 9I could i be energized while the pin III was'so held in actuated position, the safety shut down latch I I5 would be ineffective to prevent repeated recyclingand consequent building up of a dangerous concentration of unburned fuel, since the latch H5 would remain out of engagement with contact carrying bar 58. This danger is removed by preventing armature 93 from moving and closing relay contacts'l03', 69 and I04, 5| as long as the thrust pin I I? is in actuated position. Referring to Fig. 9, when therelay 9| is energized, armature 93 is pulled downwardly and the bar H3 thereupon depresses the free end of resilient member I23 slightly. With pin II! in its actuated position, engaging resilient member I23 (see Fig. 10), the effective length of the resilient member is reduced and a much greater force is necessary to depress its free'ehd an amount sufficient to allow armature 93 to move to relay energized position. RelayQI is incapable of supplying this greater force and consequently armature 93 will not move to close relay contacts I03, 69 and I04, H as long as pin I I! is engagingresilient member I23, and thus the burner and igniter remain inoperative until pin H7 is released. Moreover, accidental bumping of the reset button while the burner is in operation will not result in the relay armature moving to deenergized positionand shutting down the burner, sincethe'forceresulting from depressing thrust pin 7, while sufficient to keep armature 93 from moving to relay energizing position, is insufficient to move armature 93 to its deenergized position so long as the relay SI remains energized.

Screw I01 engages the underside of the upwardly bent member I08 on the arm Bleach time armature93 moves to"'its deenergized position, such movement of screw I01 being eifective to move arm'8'l counter-clockwise to the position shown in Fig. 4, that'is, away from and out of engagementwith the free end of bar 58. This coaction between screw I01 and member 108 affords still another'safety feature in that should the combustion responsive device fail to operate on cooling, arm '8I will not remain in engagement with the free end of bar 58, to render the safety shutdown latch H5 ineffective. Magnet III is provided for the purpose of pulling armature 93 into itsdeenergized position with sufficient force to effect the movement of arm ,8I just'described." Ambient temperature compensation or compensation for fluctuations of the temperature of the space surrounding the" control device is provided by the rear temperature responsive member 21 (see Figfil). A change in ambient temperature, for example an increase in ambient temperature, will tend to move leg 28 of member 26 to the left (as viewed in Fig. 1'). The increase in ambient temperature will also tend to move leg 3| of member 21 to the left. However, spring 2| is strong enough to hold'leg 3i against the stop I9. Consequently, leg 30 will move to the right (as viewed in Fig. 1). This movement to the right of leg 30 will be transmitted to legs 28 and 29 of member'26, since legs 29 and 30 of members 26 and 21 respectively are fastened together by plate 23. Leg '28 of member 25 will consequently be held in substantially the same position relative to fixed contacts 46 at any ordinary ambient temperature. 7 j j In addition to affording the safety features hereinabove pointed out in connection with the described mode of operation, a construction and combination of parts conforming with the present invention affords a durable 'and compact mechanism for safely and efiiciently effecting the timed ignition and recycling operation with but a, few simple control elements which can be readily manufactured at a competitive cost and assembled and calibrated with a minimum of time, effort, and skill.

Moreover, it should be apparent that certain 'of'the features of construction and certain of the combinations of parts herein disclosed are in general applicable to combustion control devices of all types, and that apparatus embodying the invention may vary considerably from that herein shown and described for purposes of illustration. It should therefore be understood that it is not intended to limit the invention-to the exact construction and/or combinations of elements shown nd described herein, as various modifications within the scope of the appended claims may occur to persons skilled in the art.

What is claimed is:

1. In a control system for a fuel burning heating apparatus including, in circuit with a power source, a means automatically positioned to'initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied and including anormally closed safety switch controlling said means, means for opening said safety switch including a movable thermally operated member, means including a combustion controlled element positionable as the result of combustion to arrest a switch opening movement'of said memher, said combustion initiating and terminating means including a part positioned to limit the switch opening movement of said member in the event such movement is arrested by said combustion controlled element and to engage and retain said member'in aposition'holding'said safety switch open in 'theevent thesw'itch opening movement of said member is not arrested by said combustion controlledf element, a heater operatively associated with said'thermally operated movable member, and controrcircuit means for said combustion heaten'andinitiating and terminating means dominated "by said safety switch.

2. In a control system for a'fuel' burning 'device including fuel'feeding and igii'ition'means, mechanism for controlling said' means comprising, in circuit with a power source, means including a relay controlled switch positionable to initiate combustion inresponse' toa demand for heat and to terminate combustion when the demand for heat is satisfied, means including a normally closed'safetysw'itch controlling energization of said relay, means for opening said safety switch inc'ludmg a thermally operated movable member, means including a combustion controlled element positionable as the result of combustion to arrest a switch opening movement of said member, a part positioned by said relay to limit the switch opening movement of said member in the event such movement is arrested by said combustion controlled element and to engage and retain-said member in a position holding said safety switch openin the event the switch opening movement of said member is not arrested by the combustion controlled element, a heater operativelyassociated with said thermally operated movable member, and control circuit means for said relay and heater dominated by said safety switch.

3. In a control system for a fuel burning heating apparatus including circuit connectionswith a power source, a first'means in said circuit automatically positioned to initiate combustion in 12 controlling said-means,- a second means for opening said safety switch including a movable thermally operated-member, means including a combustion controlled element positionable as a result of combustion to arrest aswitch opening movement of said member, said first means including a part movable therewith into and out of the-path of movement of said member to limit the-switch opening movementof said member in the event such movement is arrested by said combustion controlled element and toengage and retain said member in a position holding said safety-switch open in the event the switch opening movement ofsaid member is not arrested by said combustion-controlled element, a heater operatively associated with said thermally operated movable member, control circuit means for said heater and said first means, a reset member manually actuable to release said first means part from latching engagement with said movable-member, and an additional part operated with said reset member constructed and arranged to render the first means incapable of initiating combusticm when the reset member is held in latch releasing position.

4.-In a control system for a fuel burning device including fuel feeding and ignition means, con trol means for controlling said means including, clrcuitconnections with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied, a normally closed safety switch controlling energization of said relay, means for opening said safety switch including a thermally operated movable-member, means including-a combustion controlled element positionable as the result of combustion to arrest a switch opening movement of said member, a part positioned by said relay to limit the switch opening movement of said member in the event such movement is arrested by said combustion controlled element and to engage and retain said member in a position holding said safety switch open in the event the switch opening movement of said memberis not arrested by the combustion controlled element, a heater operatively associated with said thermally operated movable member, control circuit means for said relay and heater dominated by said safety switch, a reset member manually actuable to release said part from latching engagement with said movable member, and means including an additional part associated with said relay positioned part and reset member in a manner such that so long as said reset member is held in its latch releasing position said relay isincapable of positioning said relay controlled switch to initiate combustion.

'5. In a control system for a fuel burning device including fuel feeding andignition means, mechanism for controlling said means including, in circuit with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied, an ignition switch controlling said ignition means, a safety switch, a movable member arranged to operate said safety switch, thermal warp element means arranged to operate said ignition switch and actuate said movable memher, said warp element means being movable sufiiciently'when heated to open said ignition switch and to effect-a safety switch opening movement of said member, a combustion responsive device including an element positioned as aresult of combustion to establish a relationship with said movable member such that said safety switch remains closed while said warp element means is heated and moves sufficiently to open said ignition switch, a part controlled by said relay for movement into a position permitting only a limited further switch opening movement of said member in the event of a power failure, a heater operatively associated with said warp element means, and a control circuit means for said relay and heater dominated by said safety switch.

6. In a control system for a fuel burning device including fuel feeding and ignition means, mechanism for controlling said means including, in circuit with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfled, an ignition switch controlling said ignition means, a safety switch, a movable member arranged to operate said safety switch, thermal warp element means arranged to operate said ignition switch and actuate said movable member, said warp element means being movable sufficiently when heated to open said ignition switch and to effect a safety switch opening movement of said member, a combustion responsive device including a stepped element positioned as a result of combustion to act as a stop for said movable member such that said safety switch remains closed while said warp element means is heated and moves sufficiently to open said ignition switch, said stepped element being constructed and controlled in a manner such that upon a failure of combustion said element is moved relative to said member first to an intermediate position which presents another step which permits switch opening movement of said member and then to a final position which permits continued movement of said member, a part controlled by said relay for movement into a position permitting only a limited further switch opening movement of said member in the event of combustion failure and a resulting movement of said element to said final position, a heater operatively associated with said warp element means, and control circuit means for said heater and relay dominated by said safety switch.

. 7. In a control system for a fuel burning device including fuel feeding and ignition means, mechanism for controlling said means including, in circuit with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied, and ignition switch controlling said ignition means, a safety switch, a movable member arranged to operate said safety switch, thermal warp element means arranged to operate said ignition switch and actuate said movable mem ber, said warp element means being movable sufficiently when heated to open said ignition switch and to effect a safety switch opening movement of said member, a combustion responsive device, a stop element having a lost motion connection with said device and positioned thereby as a result of combustion to arrest movement of said movable member so that said safety switch remains closed while said warp element is heated and moves sufliciently to open said ignition switch, a first means controlled by said relay for movement into a position permitting only a limited further switch opening movement of said member in the event of a power failure,

a second means controlled by said relay and in cluding a projection engageable with a portion of said stop element to positively move the latter to a position removing the stop between said device and member whenever said relay is deenergized, a heater operatively associated with said warp element means, and control circuit means for said relay and heater dominated by said safety switch.

, 8. In a control system for a fuel burning device including fuel feeding and ignition means, mechanism for controlling saidmeans including, in circuit with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied, an ignition switch controlling said ignition means, a safety switch, a movable member arranged to operate said safety switch, thermal warp element means arranged to operate said ignition switch and actuate said movable member, said warp element means being movable sufficiently when heated to open said ignition switch and to effect a safety switch opening movement of said member, a combustion responsive device including an element positionable as a result of combustion to engage said movable member and establish a relation therewith such that said safety switch remains closed while said warp element means is heated and moves sufliv ciently to open said ignition switch, said combustion device element being held out of engagement with said movable member in the event combustion is not initiated, a part mechanically connected with said relay for movement into a position retainably engaging said member in response to the latter moving sufficiently to open said safety switch as a result of failure to initiate combustion, a heater operatively associated with said warp element means, and control circuit means for said relay and heater dominated by said safety switch.

9. In a control system for a fuel burning device including fuel feeding and ignition means, mechanism and circuits for controlling said means including, in circuit with a power source, a relay controlled switch positionable to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied, an ignition switch in the circuit for said ignition means and disposed in controlled relation with respect to said relay switch, a safety switch arranged to control said relay, a movably mounted member for operating said safety switch, thermal warp element means arranged to operate said ignition switch and actuate said movably mounted member, said warp element means being movable sufliciently when heated to open said ignition switch and to effect a safety switch opening movement of said member, a combustion responsive device including an element positionable as a result of combustion to engage said movable member and establish a relationship with said device and movable me1nber such that said safety switch remains closed while said warp element is heated and moves sufficiently to open said ignition switch, said combustion device element being normally held out of engagement with said movable member in the event combustion is not initiated and being provided with stop steps positioned relative to said member to permit a further step-by-step switch opening movement of the latter, a part connected with said relay for movement. into a position permitting only a limited further switch asset is opening movement of said -=member in the event of --combustion'- failure anda resulting movement of said element to terminate said-relationshipbetween said'deV-iceand member, said part being constructed and arranged retainably to engage said -inember in the event the latter opens said safety switch upon failure toinitiatecoinbustion, a heater bperatively -associated with -said warp element means, and control circuit -'means for said relay and heater dominated by said safety switch.

-10. 'In a control systemfor a fuel burning heating apparatus including in circuit with a power source, a first means automatically positioned to'initiate combustion in-response to a demand for h'eat and to terminate combustion when the demand for-heat'is satisfied,a safety switch controlling said means, asecond means for opening said safety switch including a-movable' member and a thermalwarpelement having a lost 1110- tion actuating connection with said member, a combustion controlled element positionable as the result of combustion to arrest a switch'opein ing'movement of saidmember, said first means including a part movable therewith and"positioned tolimit the switch opening-movement of said "member in the event such'movement is arrested by said combustion --controlled element and to engageand'retain said member in aposition holding said safety switch open in the event the switch opening movement of said member isnot arrested by saidcombustion controlled element-aheateroperativelyassociated with said warp element, control circuit means for said first means and heater dominated by said safety 7 switch, 'a reset mechanism for releasing said first meanspart from latching engagement with said "movable member, said reset mechanism comprising a "manually movable thrust pin, a

resilient'lever arranged to oppose' movement of 1' the 'first m'eans, said thrustpin being arranged to engage said resilient lever upon-manual-actu-- ation "of said resetting mechanism thereby changing the effectiveness'of said resilient lever in'opposing'movement of "said first means and rendering said first means incapable of being positioned to initiate combustion so long assaid reset mechanism is held in actuated position.

11/111 acon'trol for fuel burning heating apparatus, the combination of, control means adapted to control said-apparatus, said control means being constructed and-arranged to provide a normal relationship between its "parts which -prmits normal operation of said apparatus, and to provide a M tween its-parts which prevents operation of said apparatus, means responsive to 'presenceor absence ofcornbustion in said apparatus for con-- trolling said control means, said responsive meansbeing constructed and arranged to cause the control 'means to assume its safety relation-- ship of parts upon. failure of combustion, reset means for returning the. controlv means from .its safety relationship of parts to-its normal, relationship of parts, said reset means includinga reset element having a normalrposition but movabletherefrom to engage .parts of -saidrrcontrol means for returning .the same to its normal relationship of parts, andimechanical means associated with said reset means for mechanically engaging parts ,of said control means, said mechanical [means .being constructed andv arranged to mechanically .disable said control means from permitting normal operation of said iety relationship bei8 apparatus when the reset element-is away from its normal-position.

12. In a control for fuel burning heating-apparatus, the combinationof main control means adapted to start and stop said apparatus in response to'demand'for heat, safety means "having a first position which permits operation of said apparatus by the main control means and having a second position which prevents operation of said apparatus by the main control-means, combustion responsive means arranged to cause said safety means to assume its second position upon failureof combustion totake-place, manual reset means for returning the safety means to 'its'first position,said manual reset'means-including a reset elementhaving a normal position but movable therefrom to engage said safety means to return it to its normal'position, a device for mechanically blocking said main control ineansina manner to'prcvent'it'from starting said apparatus, and means for conditioning said devicefor blocking action when the reset element is moved away from its normal position.

'13. In acontrol for fuel burning heating-apparatus, thecombinationof, a relay adapted to start and *stop said apparatus, a safety switch having afirstposition which permits "the're lay to start the apparatus and a second position which prevents the relay from starting theapparatu's, means including combustion responsive means arranged tocause'the safety switch to assume its second position upon failure of combustion to take place, means for causing'said safety switch to remain in such position until manually reset, a manual reset element having'a normal position but movable therefrom to reset said safety switch, a device for mechanically blocking the relay to prevent it from startingthe heating apparatus, and means-for conditioning said-device for blocking action when the reset element is moved away from its normal position.

14. In a safety control adapted to control a power operated device, the combination of,'contr'ol means adapted to control said power operi ated device, said control means being constructed and arranged to have a normal relationship between its parts for permitting normal operation of said power operated device and a safety relationship preventing normal operation of said power operated deviceyresponsive means adapted to respond to an operating condition for said power operated device for controlling said control-means, saidresponsive means being constructed and arranged to cause said control means to assume its safety relationship upon the occurrence of an improper operating conditionfor said power operated device, reset means for returning the control means from its safety relationship to its normal relationship, said reset means including a reset element biased in one direction butmovable in another direction against its bias to engage parts of said control means for returning the same to its normal relationship, and mechanical means associated with said reset meanstfor mechanically engaging parts of said control means, said=mechanical means being constructed and arranged to mechanically disable said controlmeans from permitting normal operations ofsaidipower operated means when the reset element is in position to return the control d'EViCBLftO its='normalrelationship.

15. In a control system for a fuel burningheating apparatus,--main control means adapted'to start and stop-said apparatus, means including asazfety switch also in control of said apparatus and arrangedwhen' in; a, first position to permit operation of said apparatus and when in a secend position to prevent operation of said'apparatus by said main control means, means including timing means tending to causemovement of the safety switch to its second position a periodof time aitenstarting of saidapparatus; by said main control means, 3 combustion responsive m ealnsacting on presence of combustio n to. prevent opening of said safety, switch by action of said timing. means, and abutment means; operated with said main controlmeans, sai d abutmerit fmea'ns being movable independently of said? combustion responsive means ;into one position, miting safety switch opening, movement by said timingmeans and into another position preventing reclosing of said safety switch.

16. In a control system for fuel burning heating apparatus, main control means adapted to start and stop said apparatus, means including timing means and combustion responsive means for stopping said apparatus automatically if combustion fails to occur, said last mentioned means including a member responsive to combustion and an element movable by said member from a cold position to a hot position when combustion occurs, and means independent of said member responsive to combustion and independent of said timing means for returning said element from its hot position to its cold position when the burner is stopped by said main control means.

17. In a control system for fuel burning heating apparatus, main control means adapted to start and stop said apparatus, means including timing means and combustion responsive means for stopping said apparatus automatically it combustion fails to occur, said last mentioned means including a member responsive to combustion and an element movable by said member from a cold position to a hot position when combustion occurs, and means controlled by said main control means upon stopping of said apparatus for returning said element to its cold position independently of said member responsive to combustion and independently of said timing means.

18. In a control system for fuel burning heating apparatus, a relay adapted to start and stop said apparatus, means including timing means and combustion responsive means for stopping said apparatus automatically if combustion fails to occur, said last mentioned means including a member responsive to combustion and an element movable by said member from a cold position to a hot position when combustion occurs, and means, independent of said member responsive to combustion and independent of said timing means, actuated by said relay for urging said element toward its cold position when the relay stops said heating apparatus.

19. In a control system for fuel burning heating apparatus, a main control means for starting and stopping said apparatus, means including secondary control means having a starting position which permits said main control means to start the apparatus and a safety position which prevents the main control means from starting the apparatus, timing means associated with said secondary control means and tending to move the same from its starting position to its safety position a period of time after the apparatus is started by said main control means, combustion responsive means, an element operated between hot and cold positions by said combustion responsive means and in its hot position mechanically arresting the action of said timing means,

1'8 nelameans -.i.- dep ndeat oiaid-co bu vn se ens and f said timing m nsv or ar ne aidie ementyfrom-its h :p on to its co d po ition when t e a par is. t pe 2Q- I-n at n rcls s sm vra u ur n de; vice 'ncluding fuel feedi ga and ignition means, m ismfor controlling said means including, in circuit with; a. power source, a relay controlled switch positionable to initiate, combustion inre as is a e an fqrlh a nd r n e combustiqn Whenthe-dem ndgfor hea is; sa isfled, an ignition switch controlling. said ignition means, a safety switch, a movablememberlarranged. to operate said safety switch, thermal warpelement means arranged to operate said ignitionswi h and actuate said m v l member, said warp element means being movable sufficiently when heated to open said ignition switch and to eflect a safety switch opening movement of said member, a combustion responsive device, a stop element having a lost motion connection with said device and positioned thereby as a result of combustion to arrest movement of said movable member so that said safety switch remains closed while said warp element is heated and moves sufficiently to open said ignition switch, said stop element being constructed and controlled in a manner such that upon a failure of combustion such element is moved relative to said member to permit a further step-by-step switch opening movement of the latter, a first means controlled by said relay for movement into a position permitting only a limited further switch opening movement of said member in the event of a power failure, second means controlled by the relay and including a projection engageable with a portion of said stop element to positively move the latter to a position terminating the connection between said device and member whenever said relay is de-energized, a heater operatively associated with said warp element means, and a control circuit means for said relay and heater dominated by said safety switch.

21. In a control system for a fuel burning apparatus including, in circuit with a power source, a means automatically positioned to initiate combustion in response to a demand for heat and to terminate combustion when the demand for heat is satisfied and including a normally closed safety switch controlling said means, means for opening said safety switch including a hinged member and a thermal warp member, a lost motion connection between said members, said lost motion connection comprising a pin pivotally mounted on one of said members and slidably connected to the other of said members and also including a spring interposed between said members for biasing them apart, a combustion responsive device, means including an element having a lost motion connection with said device and positioned thereby as a result of combustion to engage said hinged member and obstruct the movement thereof.

22. In a control for fuel burning heating apparatus, the combination of, control means adapted to control said apparatus, said controlv means including a latching member and a movable member and being constructed and arranged to provide a normal relationship between said latching member and said movable member which permits normal operation of said apparatus, and to provide a safety latching relationship between said latching member and said movable member, means responsive topresence or absence of combustion in said apparatus for controlling said 19 control means, said responsive means being con- 'structed and arranged to cause the control means to assume its said safety latching relationship of parts upon failure of combustion, reset means for returning the control means from its said safety latching relationship of parts to its said normal relationship of parts, said reset means including a reset member manually actuable to release said movable member from latching relationship with said latching member, and means including an additional resilient part operatively associated with said latching member and said reset memberin a manner such that so long as said-reset member is held in latch releasing position said control means is mechanically disabled from permitting normal operation of said apparatus.

I 7 JOHN L. HARRIS.

RErsanNcas' crrED Number UNITED, STATES PATENTS Name a Date McCabe Jan. 10, 1,939 Marvin et a1 Dec. 19, 1939 Wallis et al. May 2 1, 1940 Dillman 1Feb. 11, 1941 Sparrow May 6, 1941 McGrath Nov. 4, 1941 Deubel June 29, 1943 Isserstedt Apr. 11, 1944 Cunningham, Sept. 24, 1946 Certificate of Correction Patent No. 2,521,717 September 12, 1950 JOHN L. HARRIS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 38, for strip 46 read strip 86; column 11, line 40, for the words combustion heater and read heater and combustion; column 13, line 57, for and ignition read an ignition; and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 5th day of December, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,521,717 September 12, 1950 JOHN L. HARRIS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 38, for strip 46 read strip 86; column 11, line 40, for the Words combustion heater and read heater and combustion; column 13, line 57, for and ignition read an ignition; and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of December, A. D. 1950.

THOMAS F. MURPI IY,

Assistant Commissioner of Patents. 

